There are known self-propelled working robots in the prior art for doing work such as cleaning the floor surface near the wall.
A working robot of this type includes a plurality of distance sensors for measuring the distance from the robot body to an obstacle. If the distance measured by the distance sensor is smaller than a predetermined threshold value, the robot is controlled so as not to collide with the wall by a predetermined avoidance operation. The threshold value is set to a predetermined constant value such that the robot will not be too far away from the wall.
Where the threshold value is not sufficiently large, however, if the inclination angle between the body and the obstacle, a side portion of the front end portion of the robot comes proximate to the obstacle even though the central head portion of the robot is not proximate to the obstacle. Then, the detection may delay, whereby the robot may collide with the obstacle.
Therefore, a primary object of the present invention is to provide a self-propelled working robot capable of precisely detecting various obstacles.
In the prior art, a working robot of this type had a problem in that it is difficult to do work on corner areas, particularly those that are not right-angled, between walls around the work area, and the work may be incomplete in such areas.
For example, while a cleaning robot disclosed in Japanese Laid-Open Patent Publication No. 9-269810 is capable of generally cleaning right-angled corner areas, the work may be incomplete in corner areas that are not right-angled. While the operation of this cleaning robot is controlled according to a pre-stored operation sequence, there is no description on the operation for completely cleaning corner areas that are not right-angled. Therefore, only with the control method disclosed therein, there may remain uncleaned portions in corner areas, Where dust collects most easily.
An autonomous traveling vehicle disclosed in Japanese Laid-Open Patent Publication No. 9-114523 is capable of traveling in parallel to a wall that is facing a side surface of the vehicle. However, as with the above cleaning robot, there may remain uncleaned portions in corner areas, where dust collects most easily.
Therefore, another object of the present invention is to provide a self-propelled working robot capable of doing work completely in corners on an area of a floor surface of the work area.
Self-propelled working robots provided with contact sensors for detecting a contact with an obstacle have been proposed in the prior art (for example, Japanese Patent No. 3201208 (FIG. 2), Japanese Laid-Open Patent Publication No. 60-206759 (FIG. 1), and Japanese Laid-Open Utility Model Publication No. 56-164602 (FIG. 5)).
However, a conventional self-propelled working robot of this type cannot appropriately and quickly perform an avoidance operation when contacting the obstacle. Thus, there are problems such as the traveling speed being significantly low or the robot being too far away from the wall.
Therefore, still another object of the present invention is to provide a self-propelled working robot capable of appropriately and quickly responding to a contact with an obstacle from any direction.
In order to achieve the primary object set forth above, a first embodiment of the present invention is directed to a self-propelled working robot, including a first distance sensor for measuring a distance to an obstacle in a front direction of the robot, and a second distance sensor for measuring a distance to the obstacle in a diagonally forward direction of the robot, the robot including: first determination means for comparing a first measured distance to the obstacle obtained by the first distance sensor with a predetermined first threshold value (SHc) to determine proximity to the obstacle; second determination means for comparing a second measured distance to the obstacle obtained by the second distance sensor with a predetermined second threshold value (SHr) to determine proximity to the obstacle; and changing means for changing the first or second threshold value (SHc or SHr) based on information regarding an inclination angle of the obstacle obtained from the first and second measured distances.
According to the present invention, the obstacle is detected by the first and second determination means, and the first threshold value or the second threshold value (SHc or SHr) is changed based on information regarding the inclination angle of the obstacle, whereby it is possible to precisely detect an obstacle even if the obstacle has a large inclination angle.
In the present invention, the information regarding the inclination angle can be obtained based on an arrangement of the first and second distance sensors, light emitting directions of the first and second distance sensors, and the first and second measured distances.
Herein, the term “front” is defined with reference to the moving direction of the working robot.
The term “the inclination angle of the obstacle obtained from the first and second measured distances” is, for example, the angle β between the normal L orthogonal to the surface of the obstacle W and the moving direction F of the present robot as shown in FIG. 5.
In a preferred embodiment of the present invention, the robot obtains a determination result from the first determination means as to proximity to the obstacle and a determination result from the second determination means as to proximity to the obstacle irrespective of a magnitude of the inclination angle, and concludes that the robot is proximate to the obstacle if either one of the two determination results indicates that the obstacle is proximate.
Where the first distance is smaller than the second distance, i.e., where the inclination angle is small, it is the first determination means, but not the second determination means, that determines that the robot is proximate to the obstacle. Where the first distance is larger than the second distance, i.e., where the inclination angle is large, it is the second determination means, but not the first determination means, that determines that the robot is proximate to the obstacle. Thus, it is possible to make a determination and conclusion as to the proximity irrespective of the magnitude of the inclination angle.
In the present invention, however, the proximity to the obstacle may be determined based on the determination result from the first determination means if the inclination angle is smaller than a predetermined value, and the proximity to the obstacle may be determined based on the determination result from the second determination means if the inclination angle is larger than a predetermined value.
Thus, by selectively using the determination result from the first determination means for a position in front of the robot and the determination result from the second determination means for a position diagonally in front of the robot based on the inclination angle of the obstacle, it is possible to detect the obstacle irrespective of the inclination angle of the obstacle.
In the present invention, the changing means sets the first threshold value or the second threshold value (SHc or SHr) so that the first or second threshold value (SHc or SHr) increases as the inclination angle increases. Thus, by increasing the first or second threshold value SHc or SHr, it is possible to detect the obstacle before a side portion of the front end portion of the robot contacts the obstacle.
In the present invention, it is preferred that the first and second distance sensors are arranged close to each other. Then, the first measured distance and the second measured distance can be compared with each other so that it is possible to detect the proximity to the obstacle based on the determination result from the first determination means if the first measured distance is smaller than the second measured distance, and to detect the proximity to the obstacle based on the determination result from the second determination means (or the first determination means) if the first measured distance is larger than the second measured distance. Thus, if the distance sensors are arranged close to each other and the first measured distance is smaller than the second measured distance, the first threshold value SHc and the second threshold value SHr may be set to the same value, for example.
Thus, by comparing the first measured distance and the second measured distance with each other, the first determination result and the second determination result can selectively be used based on the inclination angle between the robot body and the obstacle, whereby it is possible to detect the obstacle irrespective of the inclination angle of the obstacle.
In the present invention, it is preferred that the first and second distance sensors are optical distance sensors; the first distance sensor is provided in a head portion of the robot located at a center of the robot in a left-right direction; a pair of the second distance sensors are provided on both sides of, and close to, the first distance sensor; and ultrasonic distance sensors for measuring a distance to the obstacle in a front direction of the robot are provided in both side portions of a front end portion of the robot, in addition to the first and second optical distance sensors.
Thus, by using ultrasonic distance sensors and optical distance sensors in combination, it is possible to more accurately detect the obstacle.
The “optical distance sensor” may be, for example, a commercially-available optical distance sensor capable of emitting light and receiving a portion of the light beam diffusively reflected off by the obstacle through a light-receiving lens, thereby measuring the distance between itself and the obstacle by triangulation.
The “ultrasonic distance sensor” may be a commercially-available ultrasonic distance sensor capable of emitting an ultrasonic wave and measuring the distance to the object by measuring the amount of time taken for the ultrasonic wave to return from the obstacle as a reflected wave.
In the present invention, it is preferred that the first and second distance sensors are optical distance sensors; the first distance sensor is provided in a head portion of the robot located at a center of the robot in a left-right direction; a pair of the second distance sensors are provided on both sides of, and close to, the first distance sensor; and a protection cover is provided in the head portion of the robot, the protection cover having a recess with three side surfaces and a ceiling surface, wherein the three sensors are closely facing the three side surfaces; and a third distance sensor is provided on an inner position opposed to the ceiling surface for measuring a distance to a position in front of, and diagonally below, the third distance sensor.
Thus, by providing the third distance sensor for detecting an object in front of, and diagonally below, the third distance sensor, it is possible to detect unevenness of the floor surface in front of the robot. Since the distance sensors are provided in the recess of the protection cover, it is possible to prevent the recess surface from being scratched.
A robot according to a second embodiment of the present invention includes: a traveling assembly having a wheel rotating on a floor surface; a working assembly for doing work on the floor, wherein the working assembly is attached to the traveling assembly so that the working assembly is movable in a left-right direction with respect to the traveling assembly; a moving mechanism for moving the working assembly with respect to the traveling assembly so as to change a positional relationship between the traveling assembly and the working assembly; a first contact sensor provided in the working assembly for detecting contact of the obstacle with a front surface of the working assembly; a second contact sensor provided in the working assembly for detecting a contact of the obstacle with a side surface of the working assembly; and control means for controlling a travel of the traveling assembly, for controlling the moving mechanism to move the working assembly left and right at a first retraction speed based on a detection signal from the first contact sensor, and for controlling the moving mechanism to move the working assembly left and right at a second retraction speed, being lower than the first retraction speed, based on a detection signal from the second contact sensor.
When the obstacle in front of the robot contacts the front surface of the working assembly while the robot is moving forward, the first contact sensor detects the contact, and the working assembly retracts at the first, higher, retraction speed either to the left or to the right, whichever direction in which the obstacle is absent, until there is no longer a contact. Thus, the robot can travel while keeping a somewhat high traveling speed.
The term “front” or “front surface” as used herein is defined with respect to the moving direction of the robot.
When the obstacle contacts the side surface of the working assembly while the robot is moving forward, the second contact sensor detects the contact, and the working assembly retracts at the second, lower, retraction speed either to the left or to the right, whichever is opposite to the obstacle, until there is no longer a contact. Therefore, the robot can travel while the working assembly is along the obstacle, whereby the working assembly will not be too far away from the wall, being the obstacle.
In the present invention, it is preferred that the control means has a function to stop the travel if a time for which a contact is being detected by the first contact sensor is longer than a predetermined time.
Then, it is possible to prevent the working robot from being broken and the obstacle from being damaged due to the contact between the working robot and the obstacle.
In the present invention, it is preferred that the predetermined time is set to a small value when a traveling speed is high, and is set to a large value when the traveling speed is low.
Then, it is possible to prevent an unnecessary stop while the robot is traveling at a low speed, and to prevent the present working robot or the obstacle from being damaged while the robot is traveling at a high speed.
In the present invention, it is preferred that when the travel is stopped upon detecting that the detection time of the first contact sensor exceeds a predetermined threshold value, the control means controls the traveling assembly and the working assembly moving mechanism so that the robot is moved back by a predetermined distance after the stop and that the working assembly is moved in the retracting direction by a predetermined distance, after which the forward travel is resumed.
Then, it is possible to prevent the robot from moving with the working assembly being in contact with the obstacle, whereby it is possible to prevent an obstacle such as a wall from being scratched by the working assembly.
In the present invention, it is preferred that when the working assembly is moved based on the detection signal from the contact sensor, the control means controls the moving mechanism so that, after both of the contact sensors no longer detect a contact, the relative position of the working assembly with respect to the traveling assembly is returned, at a return speed being lower than the second retraction speed, to the previous position taken before the contact is detected by the contact sensor.
Then, it is possible to reduce the impact of the contact between the obstacle and the working assembly while the working assembly returns to the original position.
In the present invention, it is preferred that the working assembly is formed generally in a rectangular shape as seen in a plan view, and the contact sensor includes a bumper surrounding the periphery of the working assembly, a detection target portion moving together with the bumper, and a detection switch for detecting the detection target portion.
Then, since the bumper is surrounding the periphery of the working assembly, it is possible to detect a contact with an obstacle by detecting the detection target portion, which moves together with the bumper.
In the present invention, it is preferred that the bumper is divided into a left bumper and a right bumper, each of which is provided with the detection target portion and the detection switch, wherein the left bumper is positioned at a predetermined leftmost position while being urged leftward by a spring force, and the right bumper is positioned at a predetermined rightmost position while being urged rightward by a spring force.
Thus, the bumper is divided into a left bumper and a right bumper, which are positioned at the leftmost position and the rightmost position, respectively, while being urged by a spring force. Thus, it is not necessary to support the bumper floating in the air, and the bumper will not be swinging left and right while the robot is traveling. Thus, it is possible to precisely detect a contact with a wall.
In the present invention, it is preferred that the bumper is divided in the left-right direction and in the front-rear direction into a front left bumper, a front right bumper, a rear left bumper and a rear right bumper, each of which is provided with the detection target portion and the detection switch, wherein the front left bumper is positioned at a predetermined leftmost and foremost position while being urged leftward and forward by a spring force, the front right bumper is positioned at a predetermined rightmost and foremost position while being urged rightward and forward by a spring force, the rear left bumper is positioned at a predetermined leftmost and rearmost position while being urged leftward and rearward by a spring force, and the rear right bumper is positioned at a predetermined rightmost and rearmost position while being urged rightward and rearward by a spring force.
By dividing a bumper in the front-rear direction and in the left-right direction into four pieces, it is possible to detect a contact with a wall in the front, rear, left and right directions.
In the present invention, it is preferred that the bumper is divided in the left-right direction and in the front-rear direction into a front left bumper, a front right bumper, a rear left bumper and a rear right bumper, each of which is provided with the detection target portion and the detection switch, wherein each of the divided bumpers is positioned by a stopper at a predetermined position while being urged by the spring force outwardly so that it can retract inwardly when contacted by the obstacle.
Thus, as the bumper is divided into four pieces, with the supporting member for each bumper being urged by the spring force into contact with the stopper, the bumper divided into small pieces can be stably supported. Therefore, even if the working section is long in the left-right direction, the bumper will not be bent.
In this case, it is more preferred that the bumpers are continuous around the four corner portions of the working assembly and are separated from one another in the front surface, the rear surface and the two side surfaces.
With the bumpers being continuous around the four corner portions of the working assembly, the four corner portions of the bumpers will not be engaged with (get caught on) the obstacle, whereby it is possible to expect the robot to travel smoothly.
Still another robot of the present invention further includes: a traveling assembly capable of rotating (turning) in place about a vertical line to a floor surface; a working assembly for doing work on the floor surface, wherein the working assembly is attached to a front or a rear of the traveling assembly; rotation angle measurement means for measuring a rotation angle of the traveling assembly about the vertical line; storage means for storing the rotation angle; a plurality of front distance measurement means provided on the traveling assembly and spaced apart from each other in a width direction of the traveling assembly for measuring a distance to an front obstacle located in a moving direction of the traveling assembly; side distance measurement means for measuring a distance to an side obstacle located sideways with respect to the moving direction of the traveling assembly; determination means for determining, based on a plurality of measured values obtained by the side distance measurement means, whether or not the traveling assembly is traveling along a side wall; and control means for controlling a traveling operation of the traveling assembly, wherein: the control means determines that, when a measured value obtained by at least one of the plurality of front distance measurement means is less than or equal to a predetermined stop limit distance (SHd), the traveling assembly is close to the front obstacle in front of the robot and stops the travel of the traveling assembly, and the control means compares the measured values of the plurality of front distance measurement means with one another to determine whether or not a difference or a ratio between measured distances to a surface of the front obstacle is within a predetermined range, wherein if it is determined that the difference or the ratio between the measured distances is outside the predetermined range, the control means controls the traveling assembly to rotate in place about the vertical line until the difference or the ratio between the measured distances is within the predetermined range, and stores in the storage means the rotation angle of the traveling assembly when the difference or the ratio falls within the predetermined range; and if it is determined by the determination means that the traveling assembly has been traveling along a side wall before the rotating operation, the control means controls a traveling operation of the traveling assembly so that the robot does work on a corner area formed by the side wall and the front obstacle in front of the robot and then travel along the front obstacle in front of the robot based on the rotation angle stored in the storage means.
In the present invention, when detecting the front obstacle that is inclined, more than a predetermined angle, with respect to the moving direction of the traveling assembly, the traveling assembly stops traveling, and the traveling assembly turns in place about the vertical line until the measured distances from the plurality of front distance measurement means become generally equal to each other. Since the inclination angle of the front obstacle with respect to the moving direction of the traveling assembly is equal to the rotation angle at the point in time when the measured distances from the plurality of front distance measurement means become generally equal to each other, it is possible to obtain the inclination angle of the front obstacle by measuring the rotation angle by using the rotation angle measurement means. By detecting the presence/absence of a side wall by using the determination means, it is possible to determine whether or not it is necessary to do work on a corner area. When it is determined that the traveling assembly has been traveling along the side wall, the traveling assembly is controlled so as to travel along the front obstacle in front of the robot after doing work on the corner area. In contrast, if it is determined that the traveling assembly is traveling at a position away from the side wall, the traveling assembly is controlled so as to start traveling along the obstacle in front of the robot immediately after the turn operation.
According to the present invention, since the traveling operation of the traveling assembly is controlled based on the inclination angle of the front obstacle and the presence/absence of the side wall, irrespective of the inclination angle of the front obstacle in front of the traveling assembly, whereby it is possible to reliably do work on a corner area formed by the side wall and the front obstacle in front of the robot. Accordingly, it is possible to completely do work on the floor surface of the work area.
In the present invention, it is preferred that, when the front distance measurement means detects the front obstacle and the traveling assembly stops, the determination means makes the above determination before the traveling assembly starts rotating in place, and if it is determined by the determination means that the traveling assembly has been traveling along the side wall before the rotating operation, the control means controls the traveling operation of the traveling assembly so as to move the center of rotation for the rotating operation a predetermined distance away from the side wall before the rotating operation.
According to this embodiment, the center of rotation for the rotating operation is shifted away from the side wall by a predetermined distance before the traveling assembly turns in place, whereby it is possible to prevent some of the front distance measurement means from erroneously measuring the distance to the side wall as the distance to the front obstacle in front of the robot during the rotating operation. Accordingly, it is therefore possible to accurately measure the inclination angle of the front obstacle in front of the robot.
In a preferred embodiment of the present invention, the front distance measurement means includes a plurality of ultrasonic sensors and a plurality of optical sensors, and the ultrasonic sensors and the optical sensors are spaced apart from one another in the width direction of the traveling assembly, respectively, wherein it is determined that the inclination of the front obstacle with respect to the moving direction of the traveling assembly is smaller than a predetermined inclination angle when the ultrasonic sensor detects an obstacle and the optical sensor detects an obstacle, and it is determined that the inclination of the front obstacle with respect to the moving direction of the traveling assembly is larger than the predetermined inclination angle when the ultrasonic sensor detects no obstacle and the optical sensor detects an obstacle.
According to this embodiment, even if the inclination angle of the front obstacle in front of the robot is larger than the predetermined inclination angle and the obstacle cannot be detected by the ultrasonic sensor, the obstacle can be detected by the optical sensor, whereby it is possible to improve the obstacle detection precision. When detecting the front obstacle and measuring the inclination angle of the front obstacle, ultrasonic sensors, which have a higher measurement precision, are primarily used, whereby it is possible to improve the precision for the measurement of the inclination angle of the front obstacle.
In the present invention, it is preferred that when the front distance measurement means includes a plurality of ultrasonic sensors and a plurality of optical sensors, the plurality of optical sensors include a sensor provided inclined at a predetermined inclination angle with respect to the moving direction of the traveling assembly.
Then, it is possible to detect an obstacle diagonally in front of the traveling assembly, thereby further improving the obstacle detection precision.
In a more specific embodiment of the present invention, the “side distance value” is stored in the storage means, wherein the side distance value is the distance to the side obstacle beside the traveling assembly calculated based on a history of measured values obtained by the side distance measurement means. Moreover, the rotation angle of the traveling assembly at the point in time when the difference or the ratio between the measured distances from the plurality of front distance measurement means falls within the predetermined range during the rotating operation for obtaining the inclination angle of the front obstacle in front of the robot is stored as the “inclination angle value”, being the inclination angle of the front obstacle, in the storage means, and the measured distance from the front distance measurement means at that point in time is stored as the “front distance value” in the storage means. The control means calculates the positional relationship between the position of the traveling assembly and the position of the intersection point between the front obstacle and the side obstacle based on the “side distance value”, the “inclination angle value” and the “front distance value”, and controls the traveling operation of the traveling assembly so as to do work on the corner area formed by the front obstacle and the side obstacle based on the positional relationship information.
Thus, it is possible to calculate the positional relationship between a non-right-angled corner area and the current position of the working robot, whereby it is possible to accurately do work on corner areas.